/* Copyright (C) 2021 Aidan Hahn
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

use crate::segment::{Ctr, Seg, Type};
use crate::error::{Traceback, start_trace};
use crate::sym::{SymTable, ValueType, Args, Symbol};
use std::rc::Rc;

const AND_DOCSTRING: &str =
    "traverses a list of N arguments, all of which are expected to be boolean.
starts with arg1 AND arg2, and then calculates prev_result AND next_arg.
returns final result.";
fn and_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, Traceback> {
    let mut type_error = false;
    let mut cursor = 0;
    let result = ast.circuit(&mut |arg: &Ctr| -> bool {
        if let Ctr::Bool(b) = *arg {
            cursor += 1;
            b
        } else {
            type_error = true;
            false
        }
    });

    if type_error {
        Err(start_trace(("and", format!("input {} not a boolean", cursor)).into()))
    } else {
        Ok(Ctr::Bool(result))
    }
}

const OR_DOCSTRING: &str =
    "traverses a list of N arguments, all of which are expected to be boolean.
starts with arg1 OR arg2, and then calculates prev_result OR next_arg.
returns final result.";
fn or_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, Traceback> {
    let mut result = false;
    let mut cursor = 0;
    let correct_types = ast.circuit(&mut |arg: &Ctr| -> bool {
        if let Ctr::Bool(b) = *arg {
            cursor += 1;
            result = result || b;
            true
        } else {
            false
        }
    });

    if !correct_types {
        Err(start_trace(("or", format!("input {} not a boolean", cursor)).into()))
    } else {
        Ok(Ctr::Bool(result))
    }
}

const NOT_DOCSTRING: &str = "takes a single argument (expects a boolean).
returns false if arg is true or true if arg is false.";
fn not_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, Traceback> {
    if let Ctr::Bool(b) = *ast.car {
        Ok(Ctr::Bool(!b))
    } else {
        Err(start_trace(("not", "input is not a bool").into()))
    }
}

const ISEQ_DOCSTRING: &str = "traverses a list of N arguments.
returns true if all arguments hold the same value.
NOTE: 1 and 1.0 are the same, but '1' 'one' or one (symbol) aren't";
fn iseq_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, Traceback> {
    let head_ctr_ref = &*ast.car;
    Ok(Ctr::Bool(
        ast.circuit(&mut |arg: &Ctr| -> bool { arg == head_ctr_ref }),
    ))
}

const TOGGLE_DOCSTRING: &str = "switches a boolean symbol between true or false.
Takes a single argument (a symbol). Looks it up in the variable table.
Either sets the symbol to true if it is currently false, or vice versa.";
fn toggle_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, Traceback> {
    let var_name: String;
    if let Ctr::Symbol(ref s) = *ast.car {
        var_name = s.clone();
    } else {
        return Err(start_trace(("toggle", "input must be a symbol").into()));
    }

    let mut sym = syms
        .remove(&var_name)
        .expect(&format!("symbol {var_name} is not defined"));
    if let ValueType::VarForm(ref var) = sym.value {
        if let Ctr::Bool(ref b) = **var {
            sym.value = ValueType::VarForm(Box::new(Ctr::Bool(!b)));
        } else {
            syms.insert(var_name, sym);
            return Err(start_trace(("toggle", "can only toggle a boolean").into()));
        }
    } else {
        syms.insert(var_name, sym);
        return Err(start_trace(("toggle", "cannot toggle a function").into()));
    }

    syms.insert(var_name, sym);
    Ok(Ctr::None)
}

const BOOLCAST_DOCSTRING: &str = "takes one argument of any type.
attempts to cast argument to a bool.
Strings will cast to a bool if they are 'true' or 'false'.
Integers and Floats will cast to true if they are 0 and false otherwise.";
fn boolcast_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, Traceback> {
    match &*ast.car {
        Ctr::Bool(_) => Ok(*ast.car.clone()),
        Ctr::String(s) => {
            if s == "true" {
                Ok(Ctr::Bool(true))
            } else if s == "false" {
                Ok(Ctr::Bool(false))
            } else {
                Err(start_trace(("bool", "string cannot be parsed as a bool").into()))
            }
        },
        Ctr::Integer(i) => Ok(Ctr::Bool(*i == 0)),
        Ctr::Float(f) => Ok(Ctr::Bool(*f == 0.0)),
        _ => Err(start_trace(("bool", format!("cannot convert a {} to a boolean",
                         ast.car.to_type())).into())),
    }
}

pub fn add_bool_lib(syms: &mut SymTable) {
    syms.insert(
        "and".to_string(),
        Symbol {
            name: String::from("and"),
            args: Args::Infinite,
            conditional_branches: false,
            docs: AND_DOCSTRING.to_string(),
            value: ValueType::Internal(Rc::new(and_callback)),
            ..Default::default()
        },
    );

    syms.insert(
        "bool".to_string(),
        Symbol {
            name: String::from("bool"),
            args: Args::Infinite,
            conditional_branches: false,
            docs: BOOLCAST_DOCSTRING.to_string(),
            value: ValueType::Internal(Rc::new(boolcast_callback)),
            ..Default::default()
        },
    );

    syms.insert(
        "or".to_string(),
        Symbol {
            name: String::from("or"),
            args: Args::Infinite,
            conditional_branches: false,
            docs: OR_DOCSTRING.to_string(),
            value: ValueType::Internal(Rc::new(or_callback)),
            ..Default::default()
        },
    );

    syms.insert(
        "not".to_string(),
        Symbol {
            name: String::from("not"),
            args: Args::Strict(vec![Type::Bool]),
            conditional_branches: false,
            docs: NOT_DOCSTRING.to_string(),
            value: ValueType::Internal(Rc::new(not_callback)),
            ..Default::default()
        },
    );

    syms.insert(
        "eq?".to_string(),
        Symbol {
            name: String::from("eq?"),
            args: Args::Infinite,
            conditional_branches: false,
            docs: ISEQ_DOCSTRING.to_string(),
            value: ValueType::Internal(Rc::new(iseq_callback)),
            ..Default::default()
        },
    );

    syms.insert(
        "toggle".to_string(),
        Symbol {
            name: String::from("toggle"),
            args: Args::Lazy(1),
            conditional_branches: true,
            docs: TOGGLE_DOCSTRING.to_string(),
            value: ValueType::Internal(Rc::new(toggle_callback)),
            ..Default::default()
        },
    );
}